This application is based on Application No. 2001-217868, filed in Japan on Jul. 18, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a stator for an alternator driven by an internal combustion engine, for example, and particularly relates to a stator winding construction of the stator for an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck, and to a method for the manufacture thereof.
2. Description of the Related Art
In recent years, compactness and high output have come to be in increasing demand in automotive alternators.
In order to achieve compactness and high output in automotive alternators, improvements in the space factor of electrical conductors housed inside a magnetic circuit of a stator, and alignment in rows and increases in density of crossover portions of a stator winding (the crossover portions outside a stator core being called coil ends) are required.
In view of these conditions, a construction has been proposed in WO 98/54823, for example, attempting to improve the space factor of the electrical conductors and to achieve alignment in rows and increases in the density of the coil ends by using short conductor segments for the electrical conductors of the stator winding.
In WO 98/54823, a stator is disclosed in which a stator winding is installed by inserting a plurality of U-shaped conductor segments having a rectangular cross-sectional shape from a first end of a stator core, then joining together end portions at the opposite end from the insertion end. Because conductor segments having a rectangular cross-sectional shape are used in this stator, the conductor segments can be housed inside the slots without gaps, enabling improvements in space factor. The stator is characterized in that a stator winding in which the coil ends are disposed regularly is formed more easily than in general conventional stators constructed by winding continuous conductor wires into an annular shape to form annular winding units, forming the annular winding units into a star shape to prepare star-shaped winding units, and installing the star-shaped winding units in the stator core. In other words, alignment in rows and increased density in the coil ends of the stator winding is achieved.
However, in the stator described in WO 98/54823, the conductor segments are prepared by bending short conductor wires having a rectangular cross-sectional shape at a central portion thereof to form the U shape. In this bending process, large stresses arises in the bent portion of the rectangular conductor wires, damaging the electrically-insulating coating covering the conductor segments and causing electrical insulation to deteriorate.
Thus, it has been proposed in Japanese Patent Non-Examined Laid-Open No. 2000-299949, for example, that a central portion only of short conductor wires having a rectangular cross-sectional shape is formed into circular cross-sectional shape, to reduce the stresses arising in the bent portion during bending in an attempt to suppress damage to the electrically-insulating coating.
FIG. 26 is a cross section showing part of a conventional stator for an automotive alternator described in Japanese Patent Non-Examined Laid-Open No. 2000-299949, for example, and FIG. 27 is a perspective showing conductor segments constituting a stator winding of the stator in FIG. 26.
In FIG. 26, a stator winding installed in slots 2a of a stator core 2 is constituted by a plurality of electrical conductors, four electrical conductors being housed in each of the slots 2a and an insulator 3 being disposed so as to surround the four electrical conductors. The four electrical conductors in each of the slots 2a are arranged in a single row inside the slot in order of Address 1, Address 2, Address 3, and Address 4 from a radially-inner side.
An electrical conductor 4a in Address 1 of a first slot 2a forms a pair with an electrical conductor 4b in Address 4 in a second slot 2a a pitch of one pole away in a clockwise direction around the stator core 2. Similarly, an electrical conductor 5a in Address 2 of the first slot 2a forms a pair with an electrical conductor 5b in Address 3 in the second slot 2a a pitch of one pole away in a clockwise direction around the stator core 2. The electrical conductors 4a, 4b, 5a and 5b forming these pairs are connected by passing through return portions 4c and 5c described below using continuous wires at a first axial end of the stator core 2.
Consequently, at the first end of the stator core 2, the continuous wire connecting the electrical conductor 4b in Address 4 and the electrical conductor 4a in Address 1 surrounds the continuous wire connecting the electrical conductor 5b in Address 3 and the electrical conductor 5a in Address 2. In other words, at the first end of the stator core 2, the return portion 5c is surrounded by the return portion 4c. Hence, at the first end of the stator core 2, a first coil end group is constructed by arranging the return portions 4c and 5c in a circumferential direction to form two layers in an axial direction.
On the other hand, the electrical conductor 5a in Address 2 of the first slot 2a forms a pair with the electrical conductor 4a in Address 1 in the second slot 2a a pitch of one pole away in a clockwise direction around the stator core 2. Similarly, the electrical conductor 4b in Address 4 of the first slot 2a forms a pair with the electrical conductor 5b in Address 3 in the second slot 2a a pitch of one pole away in a clockwise direction around the stator core 2. The electrical conductors 4a, 4b, 5a and 5b forming these pairs are connected by joining at a second axial end of the stator core 2.
Consequently, at the second end of the stator core 2, outer joint portions connecting the electrical conductor 4b in Address 4 and the electrical conductor 5b in Address 3, and inner joint portions connecting the electrical conductor 4a in Address 1 and the electrical conductor 5a in Address 2 are arranged in a mutually offset state in a radial direction and circumferential direction. Hence, at the second end of the stator core 2, a second coil end group is constructed by arranging the outer joint portions and the inner joint portions in two rows in a circumferential direction so as to form a single row in a radial direction.
As shown in FIG. 27, the electrical conductor 4a in Address 1 and the electrical conductor 4b in Address 4 are furnished by a large segment 4 in which a short conductor wire is formed into a U shape, and the electrical conductor 5a in Address 2 and the electrical conductor 5b in Address 3 are furnished by a small segment 5 in which a short conductor wire is formed into a U shape. Each of the segments 4 and 5 are provided with portions which extend in an axial direction so as to be housed inside the slots 2a, and are also provided with inclined portions 4f, 4g, 5f, and 5g extending so as to be inclined at a predetermined angle relative to the axial direction and return portions 4c and 5c connecting the inclined portions 4f, 4g, 5f, and 5g. First coil ends extending outward at the first axial end surface of the stator core 2 are formed by the inclined portions 4f, 4g, 5f, and 5g and the return portions 4c and 5c. 
At the second end of the stator core 2, the projecting ends of the large segments 4 are bent away from each other, and the projecting ends of the small segments 5 are bent toward each other. The inner joint portions are formed by joining together large-segment end portions 4d and small-segment end portions 5d by welding, and the outer joint portions are formed by joining together large-segment end portions 4e and small-segment end portions 5e by welding. Hence, second coil ends extending outward at the second axial end surface of the stator core 2 are formed by inclined portions 4h, 4i, 5h, and 5i, the inner joint portions joining the large-and small-segment end portions 4d and 5d, and the outer joint portions joining the large-and small-segment end portions 4e and 5e. 
Moreover, the large segments 4 and the small segments 5 are formed by plastically deforming a central portion of short conductor wires having a rectangular cross section (a flat cross section) into a circular cross section and are then bent into a general U shape, only the return portions 4c and 5c being formed with a circular cross section, the remaining portions being formed with a rectangular cross section.
In the conventional stator described in WO 98/54823, because the conductor segments have a flat cross-sectional shape, improvement of the space factor of the electrical conductors, and alignment in rows and increased density of the coil ends are made possible, enabling compactness and high output to be achieved in an automotive alternator, but when the short conductor wires having a flat cross-sectional shape are bent into the U shape, large stresses arise in the bent portion, and one problem has been that the electrically-insulating coating covering the bent portion is damaged, making electrical insulation poor. In addition, when the coil ends come into contact with each other during assembly of the stator winding or due to vibrations generated during operation of an actual machine mounted with the stator, the corner portions of the conductor segments rub against each other, or the corner portions rub against the flat surfaces, and another problem has been that damage is caused to the electrically-insulating coating, also making electrical insulation poor.
In the conventional stator described in Japanese Patent Non-Examined Laid-Open No. 2000-299949, because the stator winding is constructed using large segments 4 and small segments 5 in which only the return portions 4c and 5c are formed with a circular cross section and the remaining portions are formed with a rectangular cross section, stresses arising in the return portions 4c and 5c when the short conductor wires are bent into the U shape are reduced, suppressing the occurrence of damage to the electrically-insulating coating covering the return portions 4c and 5c. However, because the inclined portions 4f, 4g, 5f, and 5g are formed with a flat cross-sectional shape, when the inclined portions 4f, 4g, 5f, and 5g come into contact with each other during assembly of the stator winding or due to vibrations generated during operation of an actual machine mounted with the stator, the corner portions of the inclined portions rub against each other, or the corner portions rub against the flat surfaces, and one problem has been that damage is caused to the electrically-insulating coating, also making electrical insulation poor.
The present invention aims to solve the above problems and an object of the present invention is to provide a stator for an automotive alternator and a method for manufacture thereof enabling compactness and high output to be achieved in the automotive alternator and also enabling electrical insulation to be improved by forming slot-housed portions of conductor wires with a flat cross-sectional shape and forming coil ends composed of inclined portions and return portions with a circular cross-sectional shape.
With the above object in view, a stator for an automotive alternator includes a stator core in which a plurality of slots are formed and a stator winding formed by installing conductor wires in the slots, the conductor wires being covered with an electrically-insulating coating. The stator winding is provided with slot-housed portions each formed with a flat cross-sectional shape, 2n of the slot-housed portions being housed in each of the slots, where n is an integer, and the slot-housed portions being arranged so as to line up in a single row in a slot depth direction inside each of the slots such that flat surfaces of the slot-housed portions are in close contact with side wall surfaces of the slots; n first coil ends each connecting in series a pair of slot-housed portions housed in different addresses relative to the slot depth direction in each pair of first and second slots separated by a predetermined number of slots by means of a continuous conductor wire having a non-flat cross section at a first axial end of the stator core; and n second coil ends each connecting in series a pair of slot-housed portions housed in different addresses relative to the slot depth direction in the each pair of first and second slots separated by the predetermined number of slots at a second axial end of the stator core. The n first coil ends are arranged at a pitch of one slot in a circumferential direction to constitute a first coil end group, and the n second coil ends are arranged at a pitch of one slot in the circumferential direction to constitute a second coil end group.
Therefore, there is provided a stator for an automotive alternator enabling compactness and high output to be achieved in an automotive alternator, and also enabling electrical insulation to be improved.
Each of the second coil ends may be formed by a continuous conductor wire having a non-flat cross section.
A cross-sectional area of the coil ends having the non-flat cross section may be larger than a cross-sectional area of the slot-housed portions.
The slot-housed portions housed in an outermost address in the slots may be formed with a cross-sectional shape in which a radius of curvature of radially-outer corner portions is greater than a radius of curvature of radially-inner corner portions.
The slot-housed portions housed in an innermost address in the slots may be formed with a cross-sectional shape in which a radius of curvature of radially-inner corner portions is greater than a radius of curvature of radially-outer corner portions.
The electrically-insulating coating on the flat surfaces of the slot-housed portions in close contact with the side wall surfaces of the slots may be formed so as to be thinner than the electrically-insulating coating on radially-outer and inner portions of the slot-housed portions.
The electrically-insulating coating of the slot-housed portions may be applied in two layers.
The electrically-insulating coating may be constituted by a lower electrically-insulating coating composed of an adhesion-enhanced resin and an upper electrically-insulating coating composed of a heat-tolerant resin.
The first and second coil end groups may be constructed such that inclined portions of the first and second coil ends inclined relative to an axial direction of the stator core are arranged so as to be placed in contact in the circumferential direction, the inclined portions being positioned between portions rising from the slot-housed portions and apex portions.
The slot-housed portions may be formed so as to have a hardness which is greater than that of inclined portions inclined relative to an axial direction of the stator core in the coil ends having the non-flat cross section, the inclined portions being positioned between portions rising from the slot-housed portions and apex portions.
An output wire of the stator winding extending outward from either of the first and second coil end groups may be formed so as to have a circular cross section.
With the above in view, a method for manufacturing a stator for an automotive alternator includes the step of preparing a strip-shaped winding unit constructed by arranging conductor wire pairs equal in number to a predetermined slot pitch so as to be offset by a pitch of one slot from each other, conductor wires in the conductor wire pairs having a non-flat cross-sectional shape covered with a first electrically-insulating coating, each of the conductor wires being formed into a pattern in which straight portions are linked by linking portions and arranged at the predetermined slot pitch and adjacent pairs of the straight portions are offset so as to alternately occupy an inner layer and an outer layer in a slot depth direction by the linking portions, and each of the conductor wire pairs being formed by arranging two of the conductor wires so as to be offset by the predetermined slot pitch from each other with the straight portions superposed. Further, the method for manufacturing a stator for an automotive alternator includes the step of preparing a winding assembly by press forming the straight portions of the winding unit into a flat cross-sectional shape. Furthermore, the method for manufacturing a stator for an automotive alternator includes the step of mounting the winding assembly into a rectangular parallelepiped laminated core by inserting the straight portions of the winding assembly into slots of the laminated core from a slot opening side. Moreover, the method for manufacturing a stator for an automotive alternator includes the step of forming a stator core by bending the laminated core mounted with the winding assembly into an annular shape, abutting end surfaces of the laminated core, and integrating the end surfaces of the laminated core by welding.
Therefore, the number of joints at the end surfaces of the stator core is significantly reduced, thereby there is provided a method for manufacturing a stator for an automotive alternator having a superior rate of production.
The step of preparing the winding assembly may use a die being provided with first press groove portions having a groove width equal to or greater than a width of the straight portions and second press groove portions having a groove width narrower than the width of the straight portions, each of the second press groove portions being disposed so as to extend continuously from one of the first press groove portions in a groove depth direction. The straight portions are deformed into the flat cross-sectional shape by housing the straight portions of the winding unit inside the first press groove portions, and then pressing the straight portions from the first press groove portions into the second press groove portions.
The straight portions of the winding assembly mounted to the laminated core housed in a deepest position in a slot depth direction in the slots may be formed with a cross-sectional shape in which a radius of curvature of corner portions on a slot bottom side is greater than a radius of curvature of corner portions on a slot opening side.
The straight portions of the winding assembly mounted to the laminated core housed in a shallowest position in a slot depth direction in the slots may be formed with a cross-sectional shape in which a radius of curvature of corner portions on a slot opening side is greater than a radius of curvature of corner portions on a slot bottom side.
The step of preparing the winding assembly may include press forming all of the straight portions of the winding unit simultaneously.
The step of preparing the winding assembly may include press forming all of the straight portions of a plurality of the winding units simultaneously.
The method for manufacturing a stator for an automotive alternator may further include the step of applying a second electrically-insulating coating on the straight portions of the winding assembly.
The first electrically-insulating coating may be an adhesion-enhanced resin, and the second electrically-insulating coating may be a heat-tolerant resin.